Production, characterization and application of keratinase from Streptomyces gulbargensis

A Streptomyces gulbargensis newly isolated, thermotolerant feather-degrading bacterial strain was investigated for its ability to produce keratinase enzyme. Maximum keratinolytic activity was observed at 45 °C and pH 9.0 at 120 h of incubation. Activity was completely stable (100%) between 30 and 45 °C and pH 7.0–9.0, respectively. Addition of starch to the growth medium affects the activity by means of increase in keratinase secretion. After seven days of cultivation, 10-fold increase (14.3 U ml−1) in keratinase activity was observed in the presence of 3 g starch (per liter) of the medium. The enzyme was monomeric and had a molecular mass of 46 kDa. The enzyme activity was significantly inhibited by CaCl2 and partly inhibited by EDTA, whereas, Na2SO3 enhance the enzyme activity by 2.9 times more. In addition, native chicken feather was completely degraded at 96 h of incubation. The results obtained showed that newly isolated strain S. gulbargensis could be a useful in biotechnology in terms of valorization of keratin-containing wastes or in the leather industry.